In graphics processing, the ability to render polygons or images which are not blurred in an easy and efficient manner is important. Previously, various techniques for rendering polygons have been implemented. These techniques include, for example, an Ordered Edge List algorithm and a Bresenham procedure, both of which are described in J. D. Foley et al., Fundamentals of Interactive Computer Graphics (1982). Other techniques are described in, for example, U.S. Pat. No. 4,763,119 entitled "Image Processing System For Area Filling Of Graphics," issued on Aug. 9, 1988, and U.S. Pat. No. 4,745,575 entitled "Area Filling Hardware For A Color Graphics Frame Buffer," issued on May 17, 1988, both assigned to International Business Machines Corporation.
In U.S. Pat. No. 4,763,119, an area fill technique for graphic images is disclosed wherein the contour lines constituting an image are given in a series of line segments and horizontal line segments are ignored. The pixels of each line segment are stored in a work memory such that each line segment is represented by one pixel per horizontal line. An even number of contour line pixels exist in each horizontal line in the work memory and, area fill can be realized by scanning each horizontal line in the memory and turning on pixel memory cells from an odd numbered contour line pixel to an even numbered contour line pixel.
In U.S. Pat. No. 4,745,575 a graphics display apparatus is described. To display shaded areas, additional control logic draws an outline of the area in an auxiliary memory using Bresenham's Algorithm. Edge filling logic consisting of Exclusive-OR gates is used to draw the filled area in the refresh buffer as the outline is read from an auxiliary memory into the refresh buffer.
In graphics processing, it is advantageous to be able to render polygons using the known X window EvenOdd fill rules, which are described in X Protocol Reference Manual for X Version 11, Volume 0 by O'Reilly & Associates, Inc (May 1990), which is hereby incorporated by reference. However, many of the previously known techniques, especially those which are mostly hardware implemented, are not capable of satisfying all of the X Window EvenOdd fill rules and others are too complex or inefficient. In addition, some of the rendering techniques are mostly software implemented and require complex data structures which are difficult to use and reduce the processing speed.
Therefore, a need exists for a polygon rendering technique which is faster and less complex than previously implemented methods. Further, there exists a need for a rendering technique which is capable of conforming to the X EvenOdd fill rules. Still further, a need exists for a method and system for rendering polygons in which the pixels on or below or to the right of the lines of the polygon are rendered. A yet further need exists for a polygon rendering technique which does not need complex data structures and is capable of being implemented mostly in hardware.